Many gun systems (e.g., medium or large caliber gun systems) use a mechanical ignition system in which a firing pin must physically strike each shell or cartridge to be fired. The force delivered by the firing pin initiates a chemical reaction within a primer. The primer emits heat that then ignites a propellant charge, the force generated from which propels a projectile from the shell or cartridge. Because such systems require numerous moveable parts and rely on physical contact, they are susceptible to rapid wear, mechanical failure, and performance deterioration over time. Moreover, because many mechanical ignition systems require the use of a specific primer or propellant, they offer limited economy and versatility during combat. The timing events required by mechanical firing mechanisms are also stringent. As a result, seemingly minor changes in material composition or identity can result in an improperly functioning gun. Notably, the primers and propellants used in many mechanical ignition systems are also sensitive and thus susceptible to accidental ignition due to unintended stimulation (e.g., shock or vibration).
In theory, medium and large caliber gun systems may also use a laser ignition system. In practice, however, such systems are often prohibitively expensive. Moreover, laser ignition systems rely on an optical viewing window through which a laser beam passes en route to a primer or propellant. The combination of heat, pressure, and propellant residue from the propellant chamber, along with the laser energy repeatedly passing through the window, can cause performance-degrading clouding, obscuration, and/or pitting of the viewing window over time. These changes can lead to line-of-sight problems and other issues that impede the effectiveness and reliability of laser ignition systems.